Thermal snap-acting switch



Fb 11, 1947 P. E. wlLLM/N THERMAL SNAP-ACTING swn'cn Filed Dec. 22, 1944 v3 Sheets-Sheet 1 9 i4 1. D mman Q 4 m v 4 9. ./lm 2 l 9 5 .1 2. 1 .l 4 md. l 5 F.. ...6 3 3 5 IS IVG m 9 S m g al z2 INVENIOR. P E. Wam-.MAN- BY' f//f/ ATTORNEY.

'F4211 1i, l9f47 P. E. WILLMAN 2,415,546

THERMAL SNAPACTING SWITCH Find Dc. 22, 1944 s Snom-shut s mmvron P. EMI: LLMAN 1s/27M ATTOR N EY Patented Feb. 11, 1947 THERMAL SNAP-ACTING SWITCH Philip E. Willman, Chicago, Ill., assignor to McGraw Electric Company, Elgin, Ill., a corporation of Delaware Application December 22, 1944, Serial No. 569,307

.6 Claims.

My invention relates to thermally-actuable switches and particularly to thermal snap-acting switches.

An object of my invention is to provide means that shall cause an increased pressure to be maintained between cooperating contacts of a toggle arm, snapeacting type switch, until the moment of disengagement between the said contacts.

Other objects of my invention will either be apparent from a description of several modifications embodying my invention or will be set out in the course of such description and particularly in the appended claims.

In the drawings,

Figure l is a full size, side elevational view of one form of device embodying my invention, the parts being shown in their cold positions,

Fig. 2 is a central, longitudinal, vertical sectional view of Fig. l, with the parts shown in their cold positions and in double size,

Fig. 3 is a side elevational view shown in double size, with the parts in their heated positions just prior to disengagement of the contacts,

Fig. 4 is a view similar to Fig. 3, showing the parts when heated and the contacts disengaged from each other,

Fig. 5 is a, full size, top plan view of Fig. l,

Figs. 6 and 'I are detailed views of the bimetallic bar spring and for plates which make the toggle connections,

Fig. 8 is a double size view on the line 8-8 of Fig. 4, showing the constru tion of the pivotal toggle connection,

Fig. 9 is a front end view showing the bimetal bar and its clips, which constitute the sockets for the toggle joint connection,

Fig. 10 is a lateral, sectional view taken on the line lil-ill of Fig. 2,

Fig. il is an enlarged plan view of the spring used in Figs. 14, 15, and 16,

Fig. 12 is an enlarged plan view of one part of the toggle connections operating in combination with the spring shown in Fig. 11,

Fig. 13 is a detailed, sectional view of the oontactor plate used in Figs. 14, l5, and 16, taken on the line |3|3 of Fig. l5,

Fig. 14 is a central, vertical, longitudinal, sectional view of another form of snap toggle switch, using the spring shown in Fig. 11, the parts be ing shown in their cold positions and on a double size scale.

Fig. l5 is a. view similar to Fig. 14. showing a l yside elevational view of the same, with the parts in heated positions, and,

Fig. 16 is atop plan View in Fig. 14 andl reduced to full of the parts shown or normal size.

Referring iirst of all to Figs. 1 to 10 inclusive, I have there shown a snap-acting toggle type switch embodying a base 2|, which is preferably made of electric-insulating material and which may be of substantially rectangular shape. On this member 2| is mounted adjacent to one end thereof, a block 23, which is also made of electric-insulating material and which has secured thereagainst, adjacent the outer surface thereof, an arm 25, which is made of bimetal. This arm has a slot or recess 2`| therein extending from the free end thereof to a point at about one-half oi' its length. I provide further a pair of pivot plates 29, substantially of U-shape, the central portion of which is of arcuate shape, while the end portions thereof are of straight or iiat shape secured to the free end portions of the sides of the bimetal bar 25 at its movable, outer end. Blmetal bar 25 is held by bolts or screws 3| extending through member 23 and into operative engagement with member 2|.

I provide a second toggle arm 33, which may be made of bimetal, but not necessarily so, said bar being also provided with a slot or recess 35 and having its sides pointed as will be noted particularly by reference to Figs. 5, 'l and 8. Each of the pivot plates 29 is provided with an indentation 31 (see Fig. 8) to receive the sharpened ends 38 of the sides of the second toggle arm 33, so as to provide a pivotal engagement therebetween.

An over-center spring 39 is positioned in the slots 21 and 35 and has its respective ends in pivotal engagement with members 25 and 38 through small openings immediately adjacent to the ends of the respective slots 2i and 3i. -This will provide a structure which, whensubiected tol changes of temperature actingupon the bimetal bar 25, will cause snapactin' `movement ot the outer end portion of the second, arm 82.

I provide a contact bridging member l i, which is insulatedly mounted on a support 43 of substantially T-shape, 4the stem of which extends througnan opening 45 in arm 3l, the stem of member 43 being relatively long, so as to provide a lost motion connection between the Contact bridging member Ii and arm 33. A Cotter pin 41 extends through the upper end of the stem. of member 43, so as to provide a lost motion connection, as noted above.

I provide a pair of iixed contacts 49. which are secured against the upper face of member 2| in laterally, spaced relation, so that they may be operatively engaged by contact bridging mem ber 4|.

I provide also a stop made of substantially member 5|, which may be L-shape, having one end portion thereof secured against theupper surface bodies a base 2| of rectangular shape and of elecof base 2| as by a pair of machine screws or bolts tric-insulating material, having a block 23 se- 53, with the other raised end portion 55 thereof cured thereto at one end thereof and having a adapted to be engaged by the end of the stem bimetal bar 25 secured against the outside surof member 43 when the contact bridging member 5 face of block 23, as by a pair of rivets 3|. I

4| is out of engagement with fixed contacts 49. provide further a second toggle arm 1|, and it I provide further, means for varying the opermay be noted that the shape of these arms is ating temperature of the assembly hereinbefore substantially the same as has been hereinbefore described, comprising a machine screw or bolt 51 set forth in combination with members 25 and extending through member 2| adjacent to the 10 33 in Figs. l to 5 inclusive. I provide further an supporting block 23 thereon, a lock nut 59 being over-center spring 39, having its ends in pivotal r-provided thereon, as well as an adjusting nut 6|, engagement with the two arms 25 and 33, all as this latter nut being positioned against the outhereinbefore noted. I provide a pair of pivot side surface of bimetal bar 25, so that the initial plates 29 on the outer ends of the sides of arm position oi bimetal bar 25, and of the second arm 15 25, so that the sharpened end portions' of bar 33 43, may be varied. As is weil known in the art, can engage the indentations in pivot plates 23. the temperature at which disengagement of the I provide an adjusting means comprising a movable and of the nxed contacts will take piace, machine screw or bolt 51, all as has been hereis decreased with a. position of the adjusting nut inbefore described in connection with the device 6| on screw 51 which is closer to the upper sur- 20 shown in Figs. l to i0 inclusive. I provide iurface of base 2|, than would be the case with such ther a stop member 13, o substantially L-shape, position of nut 6| further away from the upper having one end portion secured against the upper surface oi base 2|. surface of base plate 2| as by a plurality of short In order to provide for a greater and apprecimachine screws 15. I provide an 'adjustable stop able contact pressure between contact bridging 25 11, constituted by a short machine screw and a member 4I and the two contacts 49, I provide a lock nut 19 thereonso as to adjust the temperleaf spring 63 having one of its ends secured as ature dierential of the device. by rivets 65 to arm 25 intermediate the ends I provide a leaf spring 8|, which has a slot 83 thereof. Leaf spring 63 is provided also with a therein extending from its left hand end portion, ,slot 61 lextending centrally and longitudinally 30 which end portion is secure-d as by rivets 84 thereof from a point near its left hand end, as against arm 25, f bimctal, adjacent its right seen in Figs. and 6. The right hand end of l hand end portion. The right hand end portion spring 63 extends to beyond the end of the second of bent and shaped spring 8| is provided with arm 33 and is provided with an indentation 69 a return bent portion 85, which is spaced from therein, which is adapted to engage the upper 35 the adjacent main pOliOn 0f Spring 3| a Incassuriace of the enlarged part of the support 43 l ured distance to receive therebetween the end of the contact bridging member 4|. Leaf spring portion of thesecond toggle arm 1| with a rela- 63 is so shaped initially as to press against the tively large amount of clearance therebetween. upper surface of member 43 when assembled as I PIOVde a CODaci bringing member 31. which shown in Figs. 1 to 4. The positions or the two 40 is adapted to be engaged with and disengaged arms 25 and 33 relatively to the spring 63 when from a pair of xed contacts 49 secured in laterthe temperature is low, that is to say at ordinary ally-spaced relatlon against the upper surface room temperature, is shown in Fig. 2 or the drawof the right hand end portion of base plate 2|. ings, while the relative positions of these various Contact bridging member 81 is secured to a supparts just before disengagement of the contact 45 port 89, of electric-insulating material, by a rivet bridging member 4| from the two fixed contacts 8| in an electrically-insulated manner relatively 49 are shown in Fig. 3 of the drawings. It is evi- 00 Spring 3|. dent that the spring 63 will press the contact Referring HOW |10 Fig- 14 0f the drawings, I bridging member 4| into close operative engagehave there shown the toggle arms 25 and 1|, L ment with the pair of contacts 49 and that the to as well as the spring il. when the temperature pressure thus provided results in an appreciable 0f the Darts iS Say that Of an Ordinary 100m contact pressure therebetween, when the bimetal and When thc Contacts are in engagement With 't bar 25 ilexes downwardly, because of the turning each other. In Fig. 15, I have ShOWn the F051- movement of arm 25 in a clockwise direction. 'GOnS 0f these VaI'iOllS parts UDOn a change 0f Fig. 4 of the drawings showsI the relative posi- 55 temperature suiilcient to cause snap-acting distions of arms 25 and 33 and of the spring 63 dur engagement of the contact bridging member 81 ing the time when the Contact bridging member from the fixed contacts 49. It is evident from an 4I has been moved upwardly with a snap action inspection of Fig. 15, that the downward moveout of engagement with the fixed contacts 49, ment. or to Put il? in Other WOrdS, the cxllre 0f from which it wm be notes that the outer eno of to toggle arm 25111 a Clockwise direction. has caused the second arm 33 has been moved upwardly into an increased pressure to be provided between the engagement with the cotter pin 41, effected by Contact bridging member 31 and the rSi" ccn- SnaD-Hcting impact 0f bar 33 against Cotter pin tacts 49, which pressure increases until just be- 41 causing snap-acting movement of the contact fore the Snap-acting dsengging mOVemenG 0f bridging member 4| out of engagement with xed 65 toggle arm 1|. It will be noted, by reference to contacts 49 against the pressure of spring 63. It Fig. 14 that toggle arm 1I is heldin engagement is also to be noted that the presence of the bent With tbc main Portion 0f Spring 3| and that leaf spring B3, as has hereinbefore been described, the Quick upward mOi/ement 0f toggle Mm 1| results in an increased and appreciable contact effeC'S disengagement 0f COIltnct bridging memu pressure between the contact bridging member 4| 70 ber 81 from contacts 49 by impact against the and the fixed contacts 49 up to the movement of return bent portion 85. The same comment apdisengagement therebetween. plies also 'to that modiiication shown in Figs. 1 Referring now to Figs. 11 to 16 inclusive, I to 10 inclusive, as will be evident from an inspechave there shown a modification of device emtion of Figs. 2 to 4 inclusive, from which it will bodying my invention. This modiiication embe noted that the second toggle arm 33 initially amano presses against the outer end of spring 63 and that upon sudden snap-acting, upward, disengaging movement of toggle arm 33, the toggle arm will move the contact bridging Imember ll by impact against the cotter pin 41.

It is obvious that the bending or ilexure of the bimetal toggle arm 25 in a clockwise direction, atten-dant upon change of temperature thereof, causes a. contact pressure between the contact bridging members and the fixed contacts, which increases as the two toggle arms become coplanar or approach a straight line relation relatively to each other, until the sudden disengagement of the contact bridging member from the fixed contacts by impact of the outer end of the second toggle arm upon the cotter pin l1 or by impact against the return bent portion 85 of the spring 8| carrying the contact bridging member.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and all such modiflcations coming clearly within the scope of the appended claims shall be considered a part of my invention.

I claim as my invention:

1. A snap-acting thermal switch structure cornprising a first toggle arm of bimetal, having one end fixed, a second toggle arm pivotally abutting the other end of the first arm, an over-center spring connecting the two arms and bridging the pivotal connection therebetween, a contact member adjacent the outer end of the second arm and adapted to be moved thereby, a iixed contact, and a leaf spring having one end thereof secured to the first toggle arm and extending along the under surface thereof and of the second toggle arm to cause increasing pressure of the contact member on the fixed contact as the two toggle arms approach a straight line relation relatively to each other.

2. A snap-acting thermal switch structure comprising a first toggle arm of bimetal, having one end fixed, a second toggle arm pivotally abutting the other end of the first arm, an over-center spring connecting the two arms and bridging the pivotal connection therebetween, a contact member adjacent the outer end of the second arm and adapted to -be moved thereby, a fixed contact, and a leaf spring having one end thereof secured to the rst toggle arm and extending along the under surface thereof and of the second toggle arm to cause increasing pressure of the contact member on the fixed Contact just prior to snap-acting disengagement therebetween.

3. A snap-acting thermal switch structure comprising a pair of toggle arms having a pivotally abutting end-to-end connection, at least one of said arms being of bimetal and having its other end fixedly supported, each of said arms having a slot in its abutting end portion, an over-center spring in said slots bridging the pivotal connection and having its ends connected to the respective arms, a fixed contact, a. movable contact having lost motion connection with the free end of the second arm, a leaf spring having one end secured to said bimetal arm intermediate its ends and extending adjacent the lower surfaces of bothsaid arms and shaped to cause the pressure of said movable contact against said fixed contact to increase as the two arms become coplanar upon change of temperature.

4. A snap-acting thermal switch structure comprising a pair of toggle arms having forked ends in pivotal abutment with each other, at least one of said arms being bimetal and having its other end iixedly supported, an over-center spring in said forked ends having its ends connected to said arms, a iixed contact, a movable contact having a lost motion connection with the outer end of the-second arm and a leaf spring having one end secured against the under surface of said one arm and extending to the outer end of the second arm and causing increasing pressure of the movable contact on the fixed contact until the instant of separation of the two contacts by operative impact of the outer end portion of the second arm therewith.

5. A snap-acting thermal switch structure comprising a pair of toggle arms having forked ends in pivotal abutment with each other, at least one of said arms being bimetal and having its other end flxedly supported, an over-center spring in said forked ends having its ends connected to said arms, a leaf spring having one end thereof secured against the under surface of said one arm and extending to the outer end of the second arm and loosely bent thereover, a fixed contact, a movable contact mounted on the outer end of said leaf spring and adapted to have its pressure on said ilxed contact caused by said spring increased until the instant 'of snap-acting separation therebetween.

6. A snap-acting thermal switch structure comprising a pair of toggle arms having forked ends in pivotal abutment with each other, at least one of said arms being bimetal and having its other end fixedly supported, an over-center spring in said forked ends having its ends connected to said arms, a leaf spring having one end thereof secured against the under surface of said one arm and extending to the outer end of the second arm and loosely bent thereover, a fixed contact, a movable contact mounted on the outer end of said leaf spring and adapted to have its pressure on said fixed contact caused by said spring increased until the instant of snap-acting separation therebetween by impact of the outer end of the second arm against the bentover portion of the leaf spring.

PHILIP E. WILLMAN.

REFERENCES CITED The following references are of record in the iileof this patent:

UNITED STATES PATENTS Number Name Date 1,390,987 Denison Sept. 20, 1921 1,855,959 Guinot Apr. 26, 1932 1,977,393 McCormick Oct. 16, 1934 2,144,120 Parks Jan. 17, 1939 

